Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$150.75	10.213%	$166.1461	$166.15	$166.15	$166.10
Purchase #2	$96.88	9.163%	$105.7571	$105.76	$105.75	$105.80
Purchase #3	$102.79	8.144%	$111.1612	$111.16	$111.15	$111.20
Purchase #4	$156.51	3.834%	$162.5106	$162.51	$162.50	$162.50
Purchase #5	$210.45	13.610%	$239.0922	$239.09	$239.10	$239.10
Purchase #6	$142.64	4.147%	$148.5553	$148.56	$148.55	$148.60
Purchase #7	$178.69	7.772%	$192.5778	$192.58	$192.60	$192.60
7 purchase totals =	$1,038.71		$1,125.8003	$1,125.81	$1,125.80	$1,125.90